past year exams 3

Question

4.1. an ISO screw thread of 3,5mm pitch has an effective diameter of 30mm. The three-wire method is used for checking the effective diameter. The best wire size method is used for the test wires. Calculate the micrometer reading over the three wires. 4.2.1. Explain, step by step, how you would go about checking the correctness of the teeth of a gear wheel, having a module of 10mm and pressure angle of 20 degrees, using a gear-tooth Vernier caliper and applying the constant-chord method of checking. 4.2.2. Make the necessary calculations for the above test by using the constant-chord method of checking. 5. a taper of 1-in-5 on the diameter that must be tested for correctness by using 18mm diameter rollers. The centre distance between the top and bottom rollers is 55mm. The taper is 80mm long. The top diameter of the taper is 50mm. Calculate from a neat construction the distance across the top and bottom rollers. 6. shoes a roller with two sets of gauge blocks of 12,75mm each. The distance from the bottom of the groove to the top face is 70mm and the included angle of the groove is 60 degrees. 6.1. draw the diagram in the answer book 6.2. use the given dimensions and calculate the diameter of the roller. 7. shows a work piece with a V-Groove which has a 60 degree inclined angle and which is 50mm in depth. 7.1. copy and label the drawing setup 7.2. use the drawing to calculate the distance “h” 7.3. describe how you would test the magnitude of the angle on the work piece 8. the arrangement of a roller with two sets of gauge blocks of 12,75mm each. The distance from the bottom of the groove to the top of face is 70mm and the included angle of groove is 60 degrees. 8.1.1. copy the diagram into your answer book 8.1.2. use the given dimensions and calculate the diameter of the roller “d” 8.2. an ISO screw thread of 4mm pitch has an effective diameter of 35mm. the three-wire method is used for checking the effective diameter. If the best wire size is used for the test wires, calculate the micrometer reading over the three wires. 9. A tapered workpiece as shown below, to be tested for accuracy, with the aid of 20mm diameter rollers each. The distance across the top pairs of rollers is 100,52mm, while the distance across the bottom pair of rollers is 84,38mm. assume that the centres of the top pair of rollers are 95,74mm apart. Calculate the ffg: 9.1. the included angle of the tapered work piece 9.2. the small diameter Y of the workpiece 9.3. the large diameter X of the work piece

Answer 1

(4.1)

The pitch of the wire = 3.5 mm

Effective diameter of the wire = 30 mm

There are three possiblity of the wire.

(i)

Maximum wire = 1.01*pitch

Max wire = 1.01 * 3.5

Max wire = 3.535 mm

(ii)

Minimum wire = 0.505*pitch

Min wire = 0.505 * 3.5

Min wire = 1.7675 mm

(iii)

Best wire = 0.577*pitch

Best wire = 0.577 * 3.5

Best wire = 2.0195 mm

If best size method is used then best size of the wire = 2.0195 mm

Best size of the wire = 2.0195 mm.

Answer 2

(4.2.2)

Module of the gear wheel m = 10 mm

Pressure angle = 20°

Using constant chord method,

Constant Chord

where m is the module.

AB = 14.76 mm.

Therefore constant chord = 14.76 mm.

 

Answer 3

(6.2)

The Diagram is drawn as follows

Let us Consider the radius of the roller be r.

Consider a part of figure from the above.

Apply the Trigonometric Rule, sin30 = (r / 70-(12.75-r))

0.5 = r / 70-(r - 12.75)

0.5(70-(r-12.75)) = r

35 - (0.5r - 6.375) = r

35 + 6.375 - 0.5r = r

41.375 = r + 0.5r

1.5 r = 41.375

r = 27.58

Diameter of the roller = 2 * 27.58 = 55.16 mm

Therefore the Diameter of the Roller is 55.16 mm.

 

Answer 4

(5)

The Taper is 1 in 5 on the diameter.

Diameter of the rollers = 18 mm

Centre distance between roller is 55 mm

Top diameter of the taper is 50 mm

Let us construct a taper with two roller on each side

First let us find the angle of the Taper

tanα = 1/5

α = tan^-1(1/5)

α = 11.30°

 

Now consider triangle XYZ then tanα = YZ / XY

Centre Distance XY = 55

YZ = XY * tanα

YZ = 55 * tan(11.30)

YZ = 10.99

Therefore the distance across the top and bottom rollers is 10.99 mm.